Angular单元测试组件是否调用Http服务方法:错误：<spyOn>：找不到要监视的对象

import { HttpClient } from '@angular/common/http';
import { MyComponent } from './my.component';

import { HttpClientTestingModule, HttpTestingController } from '@angular/common/http/testing';

beforeEach(async(() => {
  TestBed.configureTestingModule({
    imports: [ HttpClientTestingModule ],
    declarations: [ MyComponent ],
  })
  .compileComponents();
}));

beforeEach(() => {
  httpTestingController = TestBed.inject(HttpTestingController);
  fixture = TestBed.createComponent(MyComponent);
  component = fixture.componentInstance;
  fixture.detectChanges();
});

it('should call Http service method', () => {
  const httpSpy = spyOn(TestBed.inject(HttpClient), 'get').and.returnValue(of({}));
  component.someMethod(); // 调用组件中的方法
  expect(httpSpy).toHaveBeenCalled();
});